Tube termination for telegraph purposes



y 1951 R. M. M. OBERMAN 2,551,694

' TUBE TERMINATION FOR TELEGRAPH PURPOSES Filed Dec. 17, 1947 Quid NLJLL- 01 Patented May 8, 1951 TUBE TERMINATION FOR TELEGRAPH PURPOSES Roelof M. M. Oberman, The Ha'gue,'Ne'therlands Application December 17, 1947, Serial No. 792,278 In the Netherlands September 9, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires September 9, 1966 7 Claims.

The invention refers to a termination for telegraph purposes, which can function as repeating coil between direct current lines, e. g. local lines and trunk lines for separated transmissionand reception way, preferably channels of voice frequency telegraph ystems.

Such a termination is known from U. S. patent application Serial No. 767,533, filed July 30, 1947.

A drawback of the arrangement in this application is that transmission to the local teleprinter is effected by interrupting the line current. This method of transmission is much worse than transmission by shortcircuiting this line. Another drawback of the mentioned arrangement is the fact that the emission of the trunk reception way to the trunk transmission way is prevented by simultaneous removal of the control grid voltage and the screen grid voltage of a tube, which may cause difficulties if these two voltages are not reduced quickly enough or non-simultaneously to zero. Further the method contained in this application has been restricted to amplitude modulated telegraph carrier systems.

The arrangements according to the invention avoids these drawbacks by applying a repeating coil containing a circuit with a current regulator tube, a picking off (finding) resistance and a battery, and a second circuit with a short-circuiting tube and another battery of oppo ite polarity,

such that the current in the first circuit has a constant value when the local line is closed, may be with the application of an auxiliary control tube, while the current in the local line is reduced to zero, or gets opposite polarity by bringin the short-cireuiting tube in conductive position. The arrangement according to the invention has the profit that owing to the absence of transition times of controlling relays a coupling with a frequency modulated telegraph carrier system is possible with a spacingand a marking frequency per channel, this being in contrast with the carrier frequency and the spacingand marking frequency which are usual in those systems.

The invention will be illustrated nearer by means of the added figure, which represents the principal diagram of a termination (hybrid coil) according to the invention. The teleprinter which in principle is represented by the transmission contacts ZC and the receiving coils OB is connected via a local line to the terminals l and 2 of the hybrid coil.

By Way of example the terminal 2 is connected to an earthed pole of the battery, while the terminal l via a current-regulator tube B3 and the series arrangement of the resistance RI and R is connected to the negative pole of the battery VI. The regulator tube B2 regulates the strength of current in this circuit at 40 ma. with the help of the control tube B2. It is also possible, however, at the cost of a separate source for screen grid voltage, to substitute the two tubes -B2 and for a pentode tube, in a manner as described in U. S. patent application Serial No. 767,533, filed July 30, 1947. The cathode of the control tube B2 is connected to a fixed voltage derived from the potentiometer RB/R l. The voltage drop across the R3 resistance is for instance 6 volts. The Rll' resistance connected in series with the potentiometer Rt/R l can for instance be the serie connected filament wires of the tubes BlB3. The control grid of the tube B2 is connected across a protecting resistance RID to a tap of the potentiometer Rl/RZ, which is so positioned that the voltage drop via the R2 resistance at a line current of 40 ma. for instance amounts to 5 volts.

In that case the B2 tube has a negative control grid bias of 1 volt.

If the line current decreases for some reason, the voltage drop via the R2 resistance will likewise decrease, the tube B2 getting a greaternegative control grid bias. Owing to thi the voltage drop via the anode resistance R9 of the tube B 2 decreases, the regulator tube B3 control grid across the protecting resistance RI! becoming more positive with regard to the cathode of this tube. In this way the regulator tube tries to compensate the originally expected current reduction in the local line. 3

A current increase in the local line has 'th reverse effect. The result of this regulating arrangement is that the voltage drop via the resistances R! and R2, when the current is flowing in the local line, is constant and independent of the local line resistance.

When the drawn teleprinter transmits by interrupting the local line in a particular rhythm by the help of the transmission contacts 20 the voltage via the series arrangement of the resistances RI plus R2 disappears in the same rhythm. The voltage drop via these resistances is used by means of the cell or diode G3 to control the generator arrangement of the tube B l.

The hybrid coil arrangement according to the invention yields the possibility of a special combination with frequency modulated voice frequency telegraph systems. As no controlling relays are applied, which possess a transition time, the fre- 3 quency' modulation can consists in the returning of a spacing frequency generator to the marking frequency.

The example of the embodiment contains a generator which is extremely suitable for this purpose; to couple back the anode to the control grid use is made in this arrangement of a number of R.-C. circuits (RE-1 and C|3) which are connected in series. The value of the resistances R5! and the condensers Cl-3 to be chosen simultaneously determines the generated frequency. This frequency can for instance be modified by connecting in parallel other resistances to one or more of these resistances. The Rlil resistance, which has been bridged by the condenser CQ, applies a negative control grid bias to the generator tube.

By the voltage drop over the resistance R3 and R4 the junction point of the resistances R5l is kept at a voltage, which for instance lies above that of the negative pole of the bat tery. The voltage drop over the resistances RI and R2 in the local line circuit varies between G and 30 volts. In one case the cell G3 is nonconductive in the other case it is conductive, so that the R8 resistance from A. C. point of view is connected parallel to the R6 resistance, changing the generator arrangement frequency with the desired amount. If this should be necessary in particular cases, more than one cell G3 and resistance R8 can be equipped between the cathode of the current regulator tube and the coupling points of the condensers of the various R.-C. parts of the generator arrangement.

Via the TRI transformer which is inserted into the anode circuit of the BI generator tube, the voice frequency alternating currents can be transmitted to the part of the voice frequency system that has not been shown. The generator arrangement frequency is detuned in the same rhythm as the local line is interrupted with the teleprinter transmission contacts.

After having been amplified and regulated at a constant level, the frequency modulated voice frequency A. C. voltages, which have been received via the trunk reception route, are applied to the terminals and 6 of the drawn circuit arrangement. This reception side consists in two transformers TR2 and TR3, which with the condensers Cl and C8 have been so tuned that the circuit Ll/Cl comes in resonance for instance on the spacing frequency, while the circuit T2 C3 reverberates at the marking frequency. The voltages applied to the secondaries of these transformers are rectified for instance with the indicated quadrangular arrangement of cells G! and G2.

The rectified voltage is smoothed a little by the filter elements C5 and Rl3, respectively CE and RM, the resistances RH: and 16 forming a loading resistance. The two resulting D. C. voltages have been so switched that dependent on the fact whether the spacing frequency or the marking frequency is received, as with respect to the cathode of the tube B4 negative or positive voltage is issued, which via the protecting resistance Hi2, which if desired can be substituted for a diode, is applied to the control grid of the tube B4.

Thereby the tube B4 changes from the nonconductive condition to the conductive condition on the rhythm of the received signals. The B l tube, the so-called short-circuiting tube is connected between the wire connected to terminal I of the local line and the positive pole of the voltage source, the negative pole of which is earthed. When the short-circuiting tube comes in the conductive condition, the cathode of this tube obtains about earth potentiality or, if desired, yet a slight positive voltage. In the first case the local line is short-circuited over a slight resistance which may be neglected for the transmission. This is the best way to transmit signals from the repeating coil to the teleprinter.

During the short-circuiting of the local line by the short-circuiting tube the current through the regulator tube remains 4O ma, so that the current through the short-circuiting tube cannot be more than 40 ma. either.

The voltage drop over the resistances Rl and R2 also remains constant, so that there is no reaction of the trunk reception channel on the trunk transmission channel.

The figure also contains a condenser C4, the function of which is the improvement of the transmission in the local line while the teleprinter is transmitting to the repeating coil.

From the given arrangement may easily be derived the arrangement based on the same principles and being intended for the repeating coil between four-wire local lines and voice frequency trunk ways with a separate transmission-and reception way.

It may be observed that the drawn repeating coil can transmit double current to the local line such as it is desired for some types of teleprinters, by enlarging the positive battery V2, so that the line is not short-circuited when the B4 tube becomes conductive, but that the local line current is inverted.

Moreover, it may be observed that the direction of the cell or diode G3 can be chosen arbitrarily, as the potentiality of the regulator tube B3 cathode can be either positive or negative with respect to the potentiality of the coupling point of the R5'! resistances during the transmission of the indicated teleprinter. It is also possible to apply various cells G3 in co-operation with appropriate resistances, one set of which is switched in for instance on a marking signal,

while the other set is just then switched off. While I have illustrated and described what I regard to be the preferred embodiment of my invention, nevertheless it will be understood that such is merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention, I claim:

1. A telegraph termination for connecting a direct current operated subscribers line with incoming and outgoing trunk lines, comprising in combination, a direct current operated subscribers line adapted to change from one condition to another; a direct current supply circuit constituting a first circuit and having means for regulating the current in said supply circuit; a second circuit adapted to short circuit said subscribers line; means for maintaining the current in said first circuit substantially constant and said second circuit in non-short circuiting condition when said line is in one condition; and means for changing the current in said first circuit and rendering said second circuit shortcircuiting when said line is in the other condition.

2. A telegraph termination for connecting a direct current operated subscribers line with incoming and outgoing trunk lines operated on voice frequencies, comprising in combination, a direct current operated subscribers line adapted to change from one condition to another; a supply circuit constituting a first circuit and including a current regulator tube, a resistor, and a first direct current source; a second circuit including a second tube and a second direct current source having a polarity opposite to the polarity of said first direct current source, both circuits being connected to said subscribers line; means for maintaining the current in said first circuit substantially constant and said second tube non-conductive when said line is in one condition; and means for changing the current in said first circuit and rendering said second tube conductive when said line is in the other condition.

3. A telegraph termination for connecting a direct current operated subscribers line with in coming and outgoing trunk lines operated on voice frequencies, comprising in combination, a direct current operated subscribers line adapted to be closed and interrupted; a first circuit including a current regulator tube, a resistor and a first direct current source; a second circuit including a second tube and a second direct current source having a polarity opposite to the polarity of said first direct current source, both said circuits being connected to said subscribers line; means for maintaining the current in said first circuit sub-- stantially constant and said second tube nonconductive when said line is closed; and means for changing the current in said first circuit and rendering said second tube conductive when said line is interrupted.

4. A telegraph termination for connecting a direct current operated subscribers line with incoming and outgoing trunk lines operating on voice frequencies, comprising in combination, a direct current line adapted to change from one condition to another; a first circuit including a current regulator tube, a resistor, and a first direct current source; a tap in said resistor; a control tube having a grid connected to said tap and an anode connected to the grid of said current regulator tube; a second circuit including a second tube and a second direct current source having a polarity opposite to the polarity of said first direct current source, both said circuits being connected to said subscribers line; means for maintaining the current in said first circuit substantially constant and said second tube nonconductive when said line is in one condition; and means for changing the current in said first circuit and rendering said second tube conductive when said line is in the other condition.

5. A telegraph termination for connecting a direct current subscribers line with incoming and outgoing trunk lines, comprising in combination, a direct current operated subscribers line adapted to change from one condition to another; a direct current supply circuit including a current regulator tube, a resistor, and a direct current source; means for connecting said supply circuit to said line; means for maintaining a substan tially constant current in said resistor when said line is in one condition; a generating arrangement connected to one end of said resistor; an impedance for changing the frequency of said generating arrangement; and a rectifier element passing current in only one direction and connecting said impedance with the other end of said resistor, said element being adapted to change the conductivity thereof when said line changes to the other condition.

6. A telegraph termination for connecting a direct current subscribers line with incoming and outgoing trunk lines, comprising in combination, a direct current operated subscribers line adapted to change from one condition to another; a direct current supply circuit including a current regulator tube, a first resistor, and a direct current source; means for connecting said supply circuit to said line; means for maintaining a substantially constant current in said first resistor when said line is in one condition; a generating arrangement connected to one end of said first resistor; a secod resistor connecting said generating arrangement and said first resistor; an impedance for changing the frequency of said gencrating arrangement; and a rectifier element passing current in only one direction and connecting said impedance "with the other end of said first resistor, said element being adapted to change the conductivity thereof when said line changes to the other condition.

'7. A telegraph termination for connecting a direct current operated subscribers line with incoming and outgoing trunk lines operating on voice frequencies, comprising in combination, a direct current operated subscribers line adapted to change from one condition to another; a supply circuit constituting a first circuit and including a first direct current source and means for regulating the current in said first circuit; a second circuit including a second tube and a second direct current source having a polarity opposite to the polarity of said first direct current source, both said first and said second circuits being connected to said line; means for maintaining the current in said first circuit substantially constant and said second tube non-conductive when said line is in one condition; and means for changing the current in said first circuit and rendering said second tube conductive when said line is in the other condition, said means for rendering said second tube conductive including a rectifying unit and a tuned network including inductances and condensers.

ROELOF M. M. OBERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,874,981 Hansell Aug. 30, 1932 2,408,794 Matte Oct. 8, 1946 2,461,456 Usselman Feb. 8, 1949 

